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Glass (GFR) and carbon fiber-reinforced (CFR) dual-cure polymer composites fabricated by UV-assisted three-dimensional (UV-3D) printing are presented. The resin material combines an acrylic-based photocurable resin with a low temperature (140 oC) thermally-curable resin system based on bisphenol A diglycidyl ether as base component, an aliphatic anhydride (hexahydro-4-methylphthalic anhydride) as hardener and (2,4,6,-tris(dimethylaminomethyl)phenol) as catalyst. A thorough rheological characterization of these formulations allowed us to define their 3D printability window. UV-3D printed macrostructures were successfully demonstrated, giving a clear indication of their potential use in real-life structural applications. Differential scanning calorimetry and dynamic mechanical analysis highlighted the good thermal stability and mechanical properties of the printed parts. In addition, uniaxial tensile tests were used to assess the fiber reinforcing effect on the UV-3D printed objects. Finally, an initial study was conducted on the use of a sizing treatment on carbon fibers to improve the fiber/matrix interfacial adhesion, giving preliminary indications on the potential of this approach to improve the mechanical properties of the 3D printed CFR components. [ABSTRACT FROM AUTHOR]

In this work a sequential interpenetrating polymer network (IPN) obtained by co-formulation of a photocurable acrylic resin with a thermocurable epoxy resin is presented and proposed as matrix for the fabrication of carbon-fiber reinforced (CFR) composite structures by means of 3D-printing technology. This approach combines the advantages of the easy free-form fabrication typical of the 3D-printing technology with the purposely customized features of the newly developed IPN material. Photocalorimetric and dynamic-mechanical analyses were performed in order to investigate the photo- and thermal-crosslinking reactions and their effect on the development of the IPN system. The IPN resin was finally loaded with carbon fibers and successfully ultraviolet-assisted (UV)-3D printed, demonstrating the possibility of fabricating CFR composite materials in 3D with excellent mechanical properties. Being the first example of direct fabrication of IPN-based composites by 3D printing, this study clearly shows the great potential of this additive manufacturing technology for advanced industrial applications. [ABSTRACT FROM AUTHOR]